Electric spark igniter for fuel-burning devices



1 June 13, 1967 A. w. LINDBERG 3,325,689 I.

ELECTRIC SPARK IGNITER FOR FUELBURNING DEVICES Filed March 25, 1964 United States Patent 3,325,689 ELECTRIC SPARK IGNITER FOR FUEL- BURNING DEVICES Allan W. Lindberg, 460 N. Taylor, Kirkwood, Mo. 63122 Filed Mar. 25, 1964, Ser. No. 354,541 13 Claims. (Cl. 317-96) This invention relates to improvements in control systems. More particularly, this invention relates to improvements in igniters for fuel-burning devices.

It is, therefore, an object of the present invention to provide an improved igniter for fuel-burning devices.

Dilferent types of igniters have been proposed for fuelburning devices; and some of those igniters have been used. One type of igniter utilizes a mechanical interrupter to enable a coil to establish an are between the electrodes of an arc gap. While igniters, which include coils and mechanical interrupters, can be manufactured economically, those igniters are not satisfactory; because mechanical interrupters can be unreliable in operation. Another type of igniter utilizes platinum wire, and that wire can adsorb gaseous fuel and become hot enough to ignite that fuel. Igniters of that type are, however, not satisfactory because they are expensive and they tend to have relatively short lives. Yet another type of igniter utilizes an electronic circuit. Igniters of that type can be made quite reliable; but those igniters are not satisfactory because they are expensive. Still another type of igniter uses a standard transformer to develop the voltage needed to establish anare between the electrodes of an arc gap. While igniters of that type are reliable, they are not satisfactory because the transformers therefor are bulky and expensive and are difficult to manufacture. As a result, prior igniters for fuel-burning devices have not been satisfactory. Consequently, it would be desirable to provide an igniter for fuel-burning devices which are compact, inexpensive, long-lived, and reliable. The present invention provides such an igniter; and it is, therefore, an object of the present invention to provide an igniter for fuelburning devices Which is compact, inexpensive, long-lived, and reliable.

The igniter provided by the present invention uses a harmonic transformer to develop the voltage needed to establish a spark between the electrodes of a spark gap, and an impedance is connected in series with the primary winding of that transformer to limit the current flowing through that primary winding. The core of the harmonic transformer of the igniter provided by the present invention is dimensioned so it is readily saturated; and that core saturates almost immediately after the start of each half-cycle of the alternating current supplied to the primary winding of that transformer. Once that core becomes saturated, during any given half-cycle of the alternating current, it remains saturated until close to the end of that half-cycle. That core becomes, once again saturated almost immediately after the start of the next-succeeding half-cycle of that alternating current; and that core then remains saturated until close to the end of that next-succeeding half-cycle. Throughout each period of time wherein the core of the harmonic transformer is saturated, there will be substantially no change in the magnetic flux in that core; and hence substantially no voltage will be induced in the secondary winding of that harmonic transformer. However, during each small fraction of a second wherein the magnetic flux in the core of the harmonic transformer decreases from the saturation level in one direction to zero and then increases to the saturation level in the opposite direction, there will be a very rapid change in the magnetic flux in the core of that harmonic transformer. The resulting rapid rate-of- 3,325,689 Patented June 13, 1967 change in magnetic flux in that core will induce a voltage in the secondary winding of the harmonic transformer; and the volt-per-turn ratio for that secondary Winding will be materially higher than the volt-per-turn ratio for the secondary winding of a standard transformer which has the same number of turns and which is wound on an identical core. As a result, the harmonic transformer provided by the present invention can develop the volt-age needed to establish a spark between the electrodes of a spark gap and yet be much smaller and much less expensive than a standard transformer supplying a similar step-up in voltage. It is, therefore, an object of the present invention to provide a harmonic transformer with a core that is so dimensioned, relative to the primary winding and circuit therefor, as to saturate immediately after the start of each half-cycle of the alternating current and to remain saturated until just before the end of that halfcycle.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description two preferred embodiments of the present invention are shown and described but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention Will be defined by the appended claims.

In the drawing:

FIG. 1 is a schematic diagram showing one embodiment of igniter that is made in accordance with the principles and teachings of the present invention,

FIG. 2 is a representation of a photograph, of the screen of an oscilloscope, showing the magnetizing current and the induced voltages in the harmonic transformer of the igniter shown in FIG. 1, and

FIG. 3 is a schematic diagram of another form of igniter that is made in accordance with the principles and teachings of the present invention.

Referring to FIG. 1 in detail, the numeral 10 generally denotes a harmonic transformer which is made in accordance with the principles and teachings of the present invention. That transformer has a primary winding 12 and a secondary winding 14 wound on the core thereof. That core is small, compared to the core of a standard transformer supplying a similar step-up in voltage; and that core will usually have only about three tenths of the amount of iron that is present in the core of a standard transformer supplying a similar step-up in voltage. Also, the total amount of copper wire used in the windings of that harmonic transformer will usually be only about one third of the total amount of copper wire used in the windings ofa standard transformer supplying a similar step-up in voltage.

In one preferred embodiment of harmonic transformer provided by the present invention, the core was made from E and I transformer laminations which were fourteen thousandths of an inch thick and which had leg widths of seventy-five hundredths of an inch; and that core had an overall thickness of seventy-five hundredths of an inch. That core was made from a grade of silicon steel which is commonly used for transformer laminations and which is identified as Transformer C steel. The primary winding had seventy turns of number thirty wire, and the secondary winding 14 had fourteen thousand turns of number forty wire.

The terminals of the secondary winding 14 of the harmonic transformer 10 are connected to electrodes 18 which are disposed within the fuel-burning device and which define a spark gap. The numerals 20 denote termi nals that can be selectively connected to a suitable source of alternating current by a switch or contacts, not shown.

In the said preferred embodiment of the present invention, the terminals 20 were selectively connected to a source of one hundred and fifteen volt, sixty cycle alternating current. A resistor 16 is connected between the upper terminal 20 and the upper terminal of the primary winding 12; and, in the said preferred embodiment of the present invention, that resistor was a one hundred ohm resistor.

The core, of the preferred embod1ment of harmonlc transformer provided by the present invention, saturates Whenever the voltage across the primary winding 12 rises to about one-fourth of the peak value of the A.C. voltage supplied to the terminals 20. Consequently, that core saturates almost immediately after the start of each halfcycle of that alternating current. Once that core becomes saturated, it remains saturated until close to the end of that half-cycleas when the voltage across the primary winding 12 falls to less than about one-fourth of the peak value of the A.C. voltage supplied to the terminals 20. That core will subsequently become saturated in the opposite direction almost immediately after the start of the next-succeeding half-cycle of the alternating current supplied to the terminals 20. Thereafter, that core will remain saturated until close to the end of that next-succeeding half-cycle of that alternating current.

Throughout each period of time wherein the core of the harmonic transformer is saturated, there will be substantially no change in the magnetic flux in that core; and hence substantially no voltage will be induced in the secondary winding 14 of that harmonic transformer even though the current in the primary winding 12 will rise to its maximum value and then fall toward zero. However, during each small fraction of a second wherein the magnetic flux in the core of the harmonic transformer 10 decreases from the saturation level in one direction to zero and then increases to the saturation level in the opposite direction, there will be a very rapid change in the magnetic flux in that core. The resulting rapid rate-ofchange in magnetic flux in that core will induce a voltage in the secondary winding 14; and the volt-per-turn ratio for that secondary winding will be materially higher than the 'volt-per-turn ratio for the secondary winding of a standard transformer which is wound on an identical core. For example, the peak volt-per-turn ratio for the second ary winding 14 of the preferred embodiment of harmonic transformer provided by the present invention is about five hundred and fifty thousandths, whereas the peak voltper-turn ratio for the secondary winding of a standard transformer which is wound on an identical core is only about one hundred and seventy thousandths.

Rapid rates-of-change in magnetic flux will occur adjacent the end of each even-numbered half-cycle and adjacent the start of the next-succeeding half-cycle as well as adjacent the end of each odd-numbered half-cycle and adjacent the start of the next-succeeding even-numbered half-cycle. Consequently, rapid rates-of-change in magnetic flux will occur twice during each cycle of the alternating current supplied to the terminals 20. Those rapid rates-of-change in magnetic flux will induce voltage pulses in the secondary winding 14 which Will be of short duration, and will thus resemble the positive-going or negativegoing components of a wave form which is a harmonic of the fundamental frequency of the alternating current supplied to the terminals 20. Such voltage pulses will have a relatively large amplitude; and that amplitude will be materially greater than the amplitude of the positivegoing and negative-going components of the output wave form developed by a standard transformer which has an identical core and which has the same number of turns in the secondary winding thereof. As a result, the preferred embodiment of harmonic transformer provided by the present invention has been able to supply a peak output voltage of seven and seven-tenths kilovolts with just fourteen thousand turns in the secondary winding 14 thereof, whereas a standard transformer which has an 4 identical core would require about forty-five thousand turns in the secondary winding thereof to provide a peak output voltage of seven and seven-tenths kilovolts.

As the core of the harmonic transformer saturates, almost immediately after the start of any given half-cycle of the alternating current supplied to the terminals 20, the impedance of that core will decrease; and hence the value of the current flowing through the primary winding 12 will increase. The resistance of the resistor 16 will limit the value of that current to a level which is sufficiently low to prevent undue heating of the harmonic transformer 10. Where desired, the primary winding 12 can be wound from resistance wire; and, where that is done, the ohmic value of the resistor 16 can be reduced. If the ohmic resistance of the wire used in forming the primary winding 12 is sufficiently great, the resistor 16 can be completely eliminated.

FIG. 2 is a representation of a photograph, of the screen of an oscilloscope, showing the magnetizing current and the induced voltages in the harmonic transformer 10. Specifically, the numeral 30 denotes a trace which represents slightly more than one-half of a cycle of the alternating current flowing through the primary winding 12 of the harmonic transformer 10. That trace is not a true sinusoid-particularly adjacent the zero cross-overs thereofbecause of the self-inductance of the turns of the primary winding 12. The numeral 32 denotes a trace which represents the voltage that is developed across the secondary winding 14 of the harmonic transformer 10. As the value of the negative-going portion of the trace 30 approaches zero, close to the end of the negative-going half cycle of the alternating current, a rapid rate-of-change will occur in the rnagnetic flux in the core of the harmonic transformer 10; and that rapid rate-of-change will initiate the positive-going voltage pulse 34 of the trace 32. As the current trace 30 passes through Zero and moves in the positive direction it will quickly saturate the core of the harmonic transformer 10; and, as that core saturates, the voltage across the secondary winding 14 will abruptly fall toward zero-as indicated 'by the steep trailing edge of the voltage pulse 34. The voltage across the secondary winding 14 will remain close to zero, until close to the end of the positive-going half-cycle of the alternating current-even though the current trace 30 will rise to a maximum and then start falling toward zero. Close to the end of the positive-going half-cycle of the alternating current, the magnetic flux in the core of the harmonic transformer 10 will fall below the saturation level; and, thereupon, a rapid rate-of-change will occur in the magnetic flux in that core. That rapid rate-of-change will initiate the negative-going pulse 36 of the trace 32. As the current trace 30 passes through zero and moves in the negative direction it will again quickly saturate the core of the harmonic transformer 10; and, as that core again saturates, the voltage across the secondary winding 14 will again abruptly move toward zero-as indicated by the steep trailing edge of the voltage pulse 36. The voltage across the secondary winding 14 will remain close to zero, until close to the end of the negative-going half-cycle of the alternating current-even though the current trace 30 will rise to a maximum in the negative direction and then move toward zero.

The voltage pulses will have short durations but sizable amplitudes. As a result, they will enable the secondary winding 14 to have the desired high volt-per-turn ratio.

Referring to FIG. 3 in detail, the numeral 40 denotes a harmonic transformer for a modified form of igniter that is made in accordance with the principles and teachings of the present invention. That harmonic transformer has a primary winding 42 and a secondary winding 44;

and, while the function and operation of the harmonic transformer 40 will be closely similar to the function and operation of the harmonic transformer 10, the core and the windings of the harmonic transformer 40 will be smaller than those of the harmonic transformer 10.

The terminals of the secondary winding 44 are connected to the electrodes 48 which define the spark gap for the igniter. The upper terminal of the primary winding 42 is connected to the upper of a pair of terminals 50 which can be selectively connected to a source of alternating current. That upper terminal of that primary winding also is connected to the upper stationary contact of a switch 58; and that switch can be the usual speed-responsive switch of a fractional horsepower induction motor 52. The main winding of that motor is connected between the lower terminal of the primary winding 42 and the lower terminal 50; and the starting winding 56 of that motor is connected between the lower fixed contact of the switch 58 and the lower terminal 50. The switch 58 will be closed whenever the motor 52 is de-energized; but it will open as soon as the rotor of that motor gets up to speed. The main winding 54 will, for the primary winding 42 of the harmonic transformer 40, perform the current-limiting function which the resistor 16 in FIG. 1 performs for the primary winding 12 of the harmonic transformer 10. The core of the harmonic transformer 40 in FIG. 3 can be smaller than the core of the harmonic transformer in FIG. I because it will have more current flowing through the primary winding thereof. Also, that core can be smaller than the core of the harmonic transformer 10 in FIG. 1 because the inductive nature of the main winding 54 causes the current flowing through the primary winding 42 to more closely resemble a sinusoid-and thus increase the rates-of-change in the magnetic flux in that core.

Whenever the terminals 50 of FIG. 3 are connected to a suitable source of alternating current, some current will flow through the switch 58 and the starting winding 56 of motor 52, while other current will flow through the primary winding 42 of harmonic transformer 40 and the main winding 54 of the motor 52. The current flowing through the primary winding 42 will, almost immediately after the start of each half-cycle of the alternating current supplied to the terminals 50, saturate the core of the harmonic transformer 40; and, once that core becomes saturated, it will remain saturated until close to the end of that half-cycle. The magnetic flux in the core of the harmonic transformer 40 will then fall to zero and will, almost immediately after the start of the next-succeeding half-cycle of the alternating current supplied to the terminals 50, saturate that core in the opposite direction. 'Throughout each period of time wherein the core of the harmonic transformer 40 is saturated, there will be substantially no change in the magnetic flux in that core; and hence substantially no voltage will be induced in the secondary winding 44 of that harmonic transformer. However, during each small fraction of a second wherein the magnetic flux in the core of the harmonic transformer 40 decreases from the saturation level in one direction to zero and then increases to the saturation level in the opposite direction, there will be a very rapid change in the mag netic flux in the core of that harmonic transformer. The resulting rapid rate-of-change in magnetic flux in that core will induce a voltage in the secondary winding 44 of the harmonic transformer 40, and the voltper-turn ratio for that secondary winding will be materially higher than the volt-per-turn ratio for the secondary winding of a standard transformer which is wound on an identical core. As the core of the harmonic transformer 40 saturates, the impedance of the primary winding 42 will decrease materially, and hence the current flowing through that primary winding will increase materially. However, the impedance of the main winding 54 of the motor 52 will be large enough to keep the current flowing through the primary winding 42 from unduly heating that primary winding. As the rotor of the motor gets up to speed, the switch 58 will automatically open and de-energize the starting winding 56.

The form of igniter shown in FIG. 3 is particularly useful with a fuel-burning device which is associated with equipment that employs a fractional horsepower induction motor. For example, the form of igniter shown in FIG. 3 is particularly useful with a fuel-burning device which is associated with a gas clothes dryer. With such an arrangement, the resistor 16 of FIG. 1 can be completely eliminated-thereby eliminating the cost plus the handling of a component and also improving the reliability of the igniter. Further, because the main winding 54 of motor 52 draws a relatively large amount of current, the core of the harmonic transformer 40 can be saturated even more quickly than can the core of the magnetic transformer 10. This means that the voltage pulses developed in the secondary winding 44 can be even narrower and of even greater amplitude than the voltage pulses developed in the secondary winding 14; and hence voltper-turn ratios are attainable which are eight times as great as the volt-per-turn ratios attainable with standard transformers that use identical cores. In addition, because the main winding 54 of motor 52 draws a relatively large amount of current, the core and the windings of the harmonic transformer 40 can be made even smaller, and thus less expensive, than the core and windings of the harmonic transformer 10.

Where the igniter of the present invention is used with a fuel-burning device that employs a solenoid-operated fuel valve, the solenoid of that valve could be wound so it could serve as the current limiter for the primary winding of the harmonic transformer. Specifically, that solenoid could be wound to pass sufiicient current to assure prompt saturation of the core of that harmonic transformer. Such an arrangement would be desirable because it would obviate the need of the resistor 16 of FIG. 1.

The harmonic transformers of the present invention are particularly useful with igniters, but they are not restricted to use with igniters. Instead, those transformers are usable wherever compact and inexpensive transformers with high step-ups in voltage are desired.

The harmonic transformer 10 of FIG. 1 has a core which is made from E and I laminations; but that harmonic transformer can be made with a core having any desired configuration. Further, if desired, the harmonic transformers 10 and 40 could be autotransformers.

With a given size and type of transformer core, there is a practical limit on the number of turns which can be wound on that core. In designing standard transformers for igniters, it is customary to select the smallest size transformer core on which it is economically practical to wind the number of turns which the secondary winding needs to provide the required output voltage. Because of the relatively low voltper-turn per unit of core area ratios of the secondary windings of standard transformers, the secondary windings of those transformers require many turns and the cores of those transformers must be large. Because of the higher volt-per-turn per unit of core area ratios of the secondary windings of harmonic transformers made in accordance with the principles and teachings of the present invention, the secondary windings of those transformers can have fewer turns and the cores of those transformers can be smaller in size than the secondary windings and cores of standard transformers.

FIG. 2 shows that the voltages induced in the secondary windings of harmonic transformers made in accordance with the principles and teachings of the present in vention are in the form of discrete pulses. However, because the voltages needed to sustain sparks are materially smaller than the voltages needed to initiate the formations of sparks, the voltages induced in the secondary windings of harmonic transformers made in accordance with the principles and teachings of the present invention tend to sustain the sparks between the electrodes 18 and 48 of the spark gaps shown by FIGS. 1 and 3 throughout the greater portions of the half-cycles of the AC. supplied to the terminals 20 and 50. As a result, the harmonic transformers made in accordance with the principles and teachings of the present invention have fuel-igniting capabilities which are comparable to those of standard transformers and which are superior to those of igniters using electronic circuits.

Where higher performance is desired, higher grade core materials can be used and different core configurations can be used. Thus, when the core of the trans-former 40 of FIG. 3 is a toroidal tape wound core of Deltamaxa high nickel alloy-the secondary winding 44 of that transformer has a desirably high volt-per-turn ratio. Specifically, with a Deltamax toroidal tape wound core which has a one-quarter square inch cross sectional area and with three and one-half amperes of sixty cycle A.C. flowing through the primary winding 42 thereof, the secondary winding 44 of transformer 40 in FIG. 3 has an induced potential of one and six-tenths volts per turn. Such a potential is approximately twenty-five times as great as the potential induced in the secondary winding of a standard transformer wound on a standard core of the same cross-sectional area.

Whereas the drawing and accompanying description have shown and described two preferred embodiments of the present invention it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

((1) terminals that are connectable to a source of alternating cur-rent, and

(e) a current-limiting impedance connected between said terminals and said primary winding to limit the current flowing through said primary winding after said core saturates,

(f) said secondary winding being connectable to said electrodes of said spark gap,

(g) said core of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the alternating current supplied to said terminals,

(h) said core thereafter remaining saturated until close to the end of said half-cycle of the alternating current,

(i) said harmonic transformer experiencing a rapid rate-of-change in magnetic flux as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said halfcycle of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current,

(3') said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop voltage pulses across said secondary winding,

(k) said voltage pulses having amplitudes greater than the amplitude of the voltage developed across the secondary winding of a standard transformer which has a secondary winding with the same number of turns wound on an identical core,

(1) said voltage pulses having steep leading and trailing edges,

(m) said voltage pulses simulating harmonics of said alternating current,

(n) said voltage pulses initiating sparks between the electrodes of said spark gap, and said spark continuing beyond the instants when said voltage pulses attain their peak amplitudes,

() said current-limiting impedance being the main winding of an electric motor, and thus being predominantly inductive in nature,

(p) said secondary winding having a greater volt-perturn ratio than the secondary winding of a standard transformer which has the same number of turns and is wound on an identical core.

2. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) terminals that are connectable to a source of alternating current, and

(f) a current-limiting impedance which is connected between said terminals and said primary winding to limit the current flowing through said primary winding after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedance are connected to said source of alternating current, whereby alternating current will fiow continuously through said primary winding throughout the operation of said igniter,

(g) said secondary winding being connectable to said electrodes of said spark gap and having sufficient turns to develop a fuel-igniting spark across said p,

(h) said core of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the current flowing through said terminals,

(i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(1') said harmonic transformer experiencing a rapid rate-of-change in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said half-cycle of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next succeeding half-cycle of the alternat ing current, to produce a large volt-per-turn output across said secondary winding,

(k) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop voltage pulses in the order of kilovolts across said secondary winding, 7

(1) said voltage pulses simulating harmonics of said alternating current,

(m) said voltage pulses initiating sparks between the electrodes of said spark gap, and said sparks continuing beyond the instants when said voltage pulses attain their peak amplitudes,

(11) said secondary winding having a greater volt-perturn ratio than the secondary winding of a standard transformer which has the same number of turns and is wound on an identical core.

3. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) terminals that are connectable to a source of alternating current, and

(f) a current-limiting impedance which is connected between said terminals and said primary Winding to limit the current flowing through said primary Winding after said core saturates, but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedance are connected to said source of alternating current, whereby alternating current will flow continuously through said primary Winding throughout the operation of said igniter,

(g) said secondary winding being connectable to said electrodes of said spark gap and having sufficient turns to develop a fuel-igniting spark across said s p,

(h) said core of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the current flowing through said terminals,

(i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(j) said harmonic transformer experiencing a rapid rate-of-change in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said halfcycle of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current, to produce a large volt-per-turn output across said secondary winding,

(k) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop voltage pulses in the order of kilovolts across said secondary winding,

(1) said voltage pulses having amplitudes greater than the amplitude of the voltage developed across the secondary winding of a standard transformer which has a secondary winding with the same number of turns wound on an identical core,

(In) said voltage pulses having steep leading and trailing edges.

4. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

*(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) terminals that are connectable to a source of alternating current, and

(f) a current-limiting impedance which is connected between said terminals and said primary winding to limit the current flowing through said primary winding after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedance are connected to said source of alternating current, whereby alternating current will flow continuously through said primary Winding throughout the operation of said igniter,

(g) said secondary winding being connectable to said electrodes of said spark gap and having sufiicient turns to develop a fuel-igniting spark across said p,

(b) said core, of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the current flowing through said terminals,

(i) said core thereafter remainingrsaturated until close to the end of said half-cycle of said current,

(j) said harmonic transformer experiencing a rapid rate-of-change in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said half-cycle l of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current, to produce a large volt-per-turn output across said secondary winding,

(k) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop voltage pulses in the order of kilovolts across said secondary winding.

5. A harmonic transformer that provides a volt-perturn ratio .for the secondary winding thereof that is greater than the volt-per-turn ratio of the secondary Winding of a standard transformer which has the same number of turns and is wound on an identical core and that comprises:

(a) a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

(d) terminals that are connectable to a source of alternating current, and

(e) a current-limiting impedance connected between said primary winding and said terminals to limit the current flowing through said primary winding after' said core saturates,

(f) said core becoming saturated shortly after the beginning of each half-cycle of the alternating current supplied to said terminals,

(g) said core thereafter remaining saturated until close to the end of said half-cycle of the alternating current,

(h) said harmonic transformer experiencing a rapid rate-of-change in magnetic flux as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said half-cycle of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current,

(i) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop shortduration, large amplitude voltage pulses across the secondary winding thereof,

(j) said voltage pulses having amplitudes greater than the amplitude of the voltage developed across the secondary winding of a standard transformer which has a secondary winding with the same number of turns wound on an identical core,

(k) said voltage pulses having steep leading and trailing edges,

(1) said voltage pulses simulating harmonics of said alternating current,

(In) said current-limiting impedance being the main winding of an electric motor, and thus being predominantly inductive in nature.

6. A harmonic transformer that provides a volt-perturn ratio for the secondary winding thereof that is greater than the volt-per-turn ratio of the secondary winding of a standard transformer which has the same number of turns and is wound on an identical core and that comprises:

(a) a saturable core,

'(b) a primary winding Wound on said core,

(c) a secondary winding wound on said core,

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) terminals that are connectable to a source of alternating current, and

(f) a current-limiting impedance which is connected between said primary winding and said terminals to limit the current flowing through said primary winding after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedance are connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said harmonic transformer,

(g) said secondary winding being connectable to a load to supply a high voltage to said load,

(h) said core becoming saturated shortly after the be- 1 1 ginning of each half-cycle of the current flowing through said terminals, (i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(j) said harmonic transformer experiencing a rapid rateof-change in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to'zero adjacent the end of said half-cycle of .the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current, to produce a large volt-per-turn output across said secondary winding,

(k) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop short-duration, large amplitude voltage pulses in the order of kilovolts across the secondary winding thereof,

(1) said voltage pulses simulating harmonics of said alternating current,

(In) said primary winding supplying to said secondary winding substantially all of .the power which is supplied to said secondary winding,

(u) said secondary winding supplying to said load substantially all of the power which is supplied to said load.

7. A harmonic transformer that provides a volt-perturn ratio for the secondary winding thereof that is greater than the volt-per-turn ratio of the secondary winding of a standard transformer which has the same number of turns and is wound on an identical core and that comprises:

(a) a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) terminals that are connectable to a source of alternating current, and

(f) a current-limiting impedance which is connected between said primary winding and said terminals to limit the current flowing through said primary winding after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedance are connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said harmonic transformer,

(g) said secondary winding being connectable to a load to supply a high voltage to said load,

(h) said core becoming saturated shortly after the beginning of each half-cycle of the current flowing through said terminals,

(i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(j) said harmonic transformer experiencing a rapid rate-of-change in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to Zero adjacent the end of said halfcycle of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current, to produce a large volt-perturn output across said secondary winding,

(k) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop shortduration, large amplitude voltage pulses in the order of kilovolts across the secondary winding thereof,

(1) said current-limiting impedance being inductive in nature.

8. A harmonic transformer that provides a volt-perturn ratio for the secondary winding thereof that is greater than the volt-per-turn ratio of the secondary winding of a standard transformer which has the same number of turns and is wound on an identical core and that comprises:

(a) a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

((1) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) terminals that are connectable to a source of alternating current, and

(f) a current-limiting impedance which is connected between said primary winding and said terminals to limit the current flowing through said primary winding after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedance are connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said harmonic transformer,

(g) said secondary winding being connectable to a load to supply a high voltage to said load,

(h) said core becoming saturated shortly after the beginning of each half-cycle of the current flowing through said terminals,

(i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(j) said harmonic transformer experiencing a rapid rate-of-ch-ange in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said half-cycle of the alternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current, to produce a large volt-per-turn output across said secondary winding,

(k) said harmonic transformer performing both a transforming function and a saturating function during each cycle of said alternating current,

(1) said secondary winding developing voltages in the order of kilovolts,

(In) said primary winding supplying to said secondary winding substantially all of the power which is supplied to said secondary winding,

(11) said secondary winding supplying to said load subitartially all of the power which is supplied to said 9. A harmonic transformer that provides a volt-perturn ratio for the secondary winding thereof that is greater than the volt-per-turn ratio of the secondary winding of a standard transformer which has the same number of turns and is wound on an identical core and that comprises:

(a) saturable core,

(b) 'a primary winding wound on said core,

(c) a secondary winding wound on said core, which is connect-able to a load, and

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) a primary circuit that includes said primary winding and that is connectable to a source of alternating current,

(f) said primary circuit including current-limiting impedance to limit the current flowing through said primary circuit after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding is connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said harmonic transformer,

g) said core becoming saturated during each cycle of said alternating current,

(h) the flux in said core rapidly changing, as said alternating current passes through zero, from saturation in one direction to saturation in the opposite direction to produce a large volt-per-turn output across said secondary winding,

(i) said harmonic transformer performing both a transforming function and a saturating function during each cycle of said alternating current,

(j) said secondary winding developing voltages in the order of kilovolts,

(k) said secondary winding supplying to said load substantially all of the power which is supplied to said load.

10. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

((1) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary wind-ing, and

(e) terminals connectable to a source of alternating current and to said primary winding,

(f) said primary winding having alternating current flowing continuously therein as long as said primary winding and said terminals are connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said igniter,

(g) said secondary winding being connectable to said electrodes of said spark gap and having sufiicient turns to develop a fuel-igniting spark across said spark gap,

(h) said core of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the current flowing through said terminals,

(i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(j) the flux in said core rapidly changing, as said alternating current passes through zero, from saturation in one direction to saturation in the opposite direction to produce a large volt-per-turn output across said secondary winding,

(k) said harmonic transformer performing both a transforming function and a saturating function during each cycle of said alternating current,

(I) said secondary winding developing voltages in the order of kilovolts.

11. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core, and

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) a primary circuit that includes said primary winding and that is connectable to a source of alternating current,

(f) said primary circuit including current-limiting impedance to limit the current flowing through said primary circuit after said core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding is connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said igniter,

(g) said current-limiting impedance being the resistance of the wire forming said primary winding,

(h) said secondary winding being connectable to said electrodes of said spark gap and having sufficient turns to develop a fuel-igniting spark across said spark gap,

(i) said core of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the current flowing through said terminals,

(j) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(k) said harmonic transformer experiencing a rapid rate-of-change in magnetic flux, as the magnetic flux in said core falls from the saturation level in one direction to zero adjacent the end of said half-cycle of the a ternating current and then rises to the saturation level in the opposite direction adjacent the start of the next-succeeding half-cycle of the alternating current, to produce a large volt-per-turn output across said secondary winding,

(1) said harmonic transformer responding to said rapid rate-of-change in magnetic flux to develop voltage pulses in the order of kilovolts across said secondary winding.

12. An igniter for a fuel-burning device which has electrodes that define a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core, and

(d) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) a primary circuit that includes said primary winding and that is connectable to a source of alternating current,

(f) said primary circuit including current-limiting impedance to limit the current flowing through said primary circuit after said 'core saturates but which permits alternating current to flow continuously through said primary winding as long as said primary winding is connected to said source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said igniter,

(g) said secondary winding being connectable to said electrodes of said spark gap and having sufficient turns to develop a fuel-igniting spark across said spark gap,

(h) said core of said harmonic transformer becoming saturated almost immediately after the start of each half-cycle of the current flowing through said terminal-s,

(i) said core thereafter remaining saturated until close to the end of said half-cycle of said current,

(i) the flux in said core rapidly changing, as said alternating current passes through zero, from saturation in one direction to saturation in the opposite direction to produce a large volt-per-turn output across said secondary winding,

(k) said secondary winding developing voltages in the order of kilovolts.

13. An igniter for a fuel-burning device which has spaced electrodes forming a spark gap and which comprises:

(a) a harmonic transformer that has a saturable core,

(b) a primary winding wound on said core,

(c) a secondary winding wound on said core,

((1) said secondary winding having more turns than said primary winding, whereby said harmonic transformer develops a stepped-up voltage across said secondary winding,

(e) a current-limiting impedance which limits primary winding current after core saturation but which permits alternating current to flow continuously through said primary winding as long as said primary winding and said current-limiting impedanceare connected to a source of alternating current, whereby alternating current will flow continuously through said primary winding throughout the operation of said igniter,

(f) a primary circuit that includes said primary Winding and said current limiting impedance and is adapted to be connected to a source of alternating current supply of higher voltage than that required to saturate said core, and

(g) a secondary circuit that includes said secondary winding and said spaced electrodes forming a spark gap and having suflicient turns to develop a fueli-gniting spar-k across said spark gap,

(h) the flux in said core rapidly changing, as said alternating current passes through zero, from saturation in one direct-ion to saturation in the opposite direction to produce a large volt-per-turn output across said secondary winding,

(i) said secondary Winding developing voltages in the order of kilovolts,

(j) said harmonic transformer performing both a transforming function and a saturating function during said cycle of said alternating current.

References Cited UNITED STATES PATENTS RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

10. AN IGNITER FOR A FUEL-BURNING DEVICE WHICH HAS ELECTRODES THAT DEFINE A SPARK GAP AND WHICH COMPRISES: (A) A HARMONIC TRANSFORMER THAT HAS A SATURABLE CORE, (B) A PRIMARY WINDING WOUND ON SAID CORE, (C) A SECONDARY WINDING WOUND ON SAID CORE, (D) SAID SECONDARY WINDING HAVING MORE TURNS THAN SAID PRIMARY WINDING, WHEREBY SAID HARMONIC TRANSFORMER DEVELOPS A STEPPED-UP VOLTAGE ACROSS SAID SECONDARY WINDING, AND (E) TERMINALS CONNECTABLE TO A SOURCE OF ALTERNATING CURRENT AND TO SAID PRIMARY WINDING, (F) SAID PRIMARY WINDING HAVING ALTERNATING CURRENT FLOWING CONTINUOUSLY THEREIN AS LONG AS SAID PRIMARY WINDING AND SAID TEMINALS ARE CONNECTED TO SAID SOURCE OF ALTERNATING CURRENT, WHEREBY ALTERNATING CURRENT WILL FLOW CONTINUOUSLY THROUGH SAID PRIMARY WINDING THROUGHOUT THE OPERATION OF SAID IGNITER, (G) SAID SECONDARY WINDING BEING CONNECTABLE TO SAID ELECTRODES OF SAID SPARK GAP AND HAVING SUFFICIENT TURNS TO DEVELOP A FUEL-IGNITING SPARK ACROSS SAID SPARK GAP, (H) SAID CORE OF SAID HARMONIC TRANSFORMER BECOMING SATURATED ALMOST IMMEDIATELY AFTER THE START OF EACH HALF-CYCLE OF THE CURRENT FLOWING THROUGH SAID TERMINALS, (I) SAID CORE THEREAFTER REMAINING SATURATED UNTIL CLOSE TO THE END OF SAID HALF-CYCLE OF SAID CURRENT (J) THE FLUX IN SAID CORE RAPIDLY CHANGING, AS SAID ALTERNATING CURRENT PASSES THROUGH ZERO, FROM SATURATION IN ONE DIRECTION TO SATURATION IN THE OPPOSITE DIRECTION TO PRODUCE A LARGE VOLT-PER-TURN OUTPUT ACROSS SAID SECONDARY WINDING, (K) SAID HARMONIC TRANSFORMER PERFORMING BOTH A TRANSFORMING FUNCTION AND A SATURATING FUNCTION DURING EACH CYCLE OF SAID ALTERNATING CURRENT, (L) SAID SECONDARY WINDING DEVELOPING VOLTAGES IN THE ORDER OF KILOVOLTS. 